The present invention generally relates to objective measurements and surgical correction of a human eye and, in particular, to systems and methods for ensuring a correct positioning of the eye for surgery.
Laser surgery on the eye using laser in situ keratomileusis (LASIK) and laser epithelial keratomileusis (LASEK) is a common type of laservision correction procedure. It has proven to be an extremely effective outpatient procedure for a wide range of vision corrective prescriptions. The use of an excimer laser allows for a high degree of precision and predictability in shaping the cornea of the eye. Prior to the LASIK procedure, measurements of the eye are made to determine the amount of corneal material to be removed from various locations on the corneal surface so that the excimer laser can be calibrated and guided for providing the corrective prescription previously determined by measurement.
Procedures such as LASIK require precise alignment between the eye and the corrective laser beam. At present the patient is requested to focus on a fixation target such as a light-emitting diode (LED), but holding the eye steady during surgery may prove difficult.
It is also known to cross narrow beams at the apex of a curved surface, for example, at the top of a cornea. If the apex of the curved surface is substantially transmissive and/or specularly reflective, the intersection of the crossed beams at the apex is difficult to discern. Further, radiation safety is of concern in applications wherein the beams are permitted to remain impinging on the surface. In addition, in applications involving several dielectric interfaces such as in the eye, multiple reflections are likely to occur, which may create confusion in observation.
Thus there is a need to provide an accurate, safe, readily discernible reference for orienting the eye for surgery.
It is therefore an object of the present invention to provide a system and method for positioning an eye for surgery.
It is a further object to provide such a system and method that are substantially noninvasive.
It is an additional object to provide such a system and method that have less potential for harming eye tissue.
It is another object to provide such a system and method that provide a continuous indication of alignment.
These and other objects are achieved by the present invention, a first aspect of which includes a system for positioning an eye for laser surgery. The system comprises a first and a second line generator positioned, respectively, to emit a first line and a second line orthogonal to the first line. The first and the second line generators are further positioned in a predetermined relation to a laser surgical system.
Means for adjusting a position of the eye are positioned along an axis that is substantially perpendicular to the first and the second line. This location is for achieving a positioning wherein the first and the second line form a cross. The location of the cross comprises a preferred position for the eye relative to the laser surgical system for the laser surgery.
The method of the present invention comprises the steps of generating a first and a second line of radiation, wherein the first line is substantially orthogonal to the second line. The first and the second lines are directed to a position having a predetermined relation to a laser surgical system. A position of an eye is then adjusted along an axis substantially perpendicular to the first and the second line to achieve a positioning wherein the first and the second line form a cross on a cornea of the eye in a plane. This plane comprises a preferred position of the eye relative to the laser surgical system for laser surgery.
In an alternate embodiment, the patient bed can remain stationary, and the surgical system translated to the desired position as determined by the system of the present invention.
In another embodiment, a system for relatively positioning an eye and a surgical system for laser surgery comprises a first and a second radiation generator positioned, respectively, to emit a first beam and a second beam. Optics means are provided for focusing the first and the second beam into a first and a second spot, respectively, on a predetermined location of an eye. The optics means are positioned in a predetermined relation to a laser surgical system.
Means are also provided for adjusting a relative position of the first and the second radiation generators, the optics means, and the eye to achieve a preferred position for laser surgery, with reference to the locations of the first and the second spot. Thus the locations of the first and the second spot on the eye and relative to each other may be used as an indicator for achieving the preferred position for laser surgery.
The features that characterize the invention, both as to organization and method of operation, together with further objects and advantages thereof, will be better understood from the following description used in conjunction with the accompanying drawing. It is to be expressly understood that the drawing is for the purpose of illustration and description and is not intended as a definition of the limits of the invention. These and other objects attained, and advantages offered, by the present invention will become more fully apparent as the description that now follows is read in conjunction with the accompanying drawing.